1. Field of the Disclosure
The present disclosure relates to a high voltage gas circuit breaker, and particularly, to a high voltage gas circuit breaker capable of enhancing a breaking performance and durability by controlling a volume of an expansion chamber by a pressing member.
2. Background of the Disclosure
A high voltage gas circuit breaker (or a high voltage gas insulated switchgear) indicates an apparatus installed on a circuit between a power side and a load side of a power system, and configured to protect the power system or a load device by switching the circuit in a normal current state, and by breaking the circuit when an abnormal current such as a ground fault and a short circuit occurs on the circuit. The high voltage gas circuit breaker is configured to separate a movable electrode from a fixed electrode by receiving power from an power unit connected to outside. In this case, an arc occurring between contacts is extinguished by gas such as SF6 sprayed thereonto.
A method for extinguishing an arc occurring from the high voltage gas circuit breaker is largely classified into a puffer method and a composite extinguishing method according to a configuration of an extinguishing unit. The puffer method indicates a method for extinguishing an arc by compressed heat gas. On the other hand, the composite extinguishing method indicates a method for extinguishing an arc using the existing puffer method and a thermal expansion method. In the composite extinguishing method, a circuit to which a small current has been applied is interrupted by the exiting puffer method, i.e., by extinguishing an arc using compressed gas. However, a circuit to which a large current has been applied is interrupted by utilizing heat gas expanded by arc energy to extinguish an arc.
FIGS. 1a, 1b, 1c and 1d illustrate an operation principle of a puffer type gas circuit breaker in accordance with the conventional art. More specifically, FIG. 1a illustrates a state of a closed circuit, FIG. 1b illustrates a state just before an open circuit, FIG. 1c illustrates an extinguished state, and FIG. 1d illustrates a state of an open circuit.
The gas circuit breaker includes a fixed arc contactor 1, a nozzle 2, a fixed contactor 3, a movable arc contactor 4, a compression chamber 5, a movable contactor 6, a fixed piston 7, and a cylinder rod 8. If the cylinder rod 8 is downward moved as shown in FIG. 1b by an adjusting force from an external driving source, from a closed state shown in FIG. 1a, the cylinder rod 8, the movable contactor 6 and the nozzle 2 are also downward moved. As a result, gas inside the compression chamber 5 is compressed. For an extinguished state (FIG. 1c), extinguishing gas (SF6) compressed in the compression chamber 5 is sprayed through the nozzle 2, thereby cool-extinguishing an arc in a blowing manner. Then the cylinder rod 8 is downward moved, so that the fixed arc contactor 1 and the movable arc contactor 4 are separated from each other (FIG. 1d).
FIGS. 2a and 2b illustrate an operation principle of a composite extinguishing type gas circuit breaker in accordance with the conventional art.
The gas circuit breaker includes a movable electrode composed of a movable rod 11 connected to an operator, a movable main contact 12, a movable arc contact 13, a main nozzle 14 and an auxiliary nozzle 15; and a fixed electrode composed of a fixed main contact 16 and a fixed arc contact 17. The gas circuit breaker also includes a compression chamber 18 for compressing extinguishing gas as the movable electrode moves; and an expansion chamber 19 for expanding gas by an arc occurring when the movable main contact 12 and the fixed main contact 16 are separated from each other. A flow path 10, through which the movable arc contact 13 and the fixed arc contact 17 are separated from each other and heat gas expanded when the main nozzle 14 is separated from the fixed arc contact 17, is formed between the main nozzle 14 and the auxiliary nozzle 15.
FIG. 2a illustrates a normal state of a circuit, i. e., a state where a current flows on a closed circuit through contacts. If a movable electrode and a fixed electrode are separated from each other as shown in FIG. 2b as an abnormal current occurs, an arc is generated between the movable arc contact 13 and the fixed arc contact 17. In this case, an expansion energy of the arc is applied to the expansion chamber 19 to thus increase a pressure inside the expansion chamber 19. If the movable arc contact 13 is separated from the fixed arc contact 17 and the main nozzle 14 is also separated from the fixed arc contact 17, extinguishing gas is sprayed onto the fixed arc contact 17 from the expansion chamber 19 and the compression chamber 18, along the flow path 10 formed between the movable arc contact 13 and the fixed arc contact 17. As a result, the arc is extinguished.
The aforementioned puffer method has an inner structure where the compression chamber 5 and the expansion chamber are integrated with each other. The puffer method is a method for extinguishing an arc by spraying heat gas of which pressure has been increased when a neck portion of the main nozzle 2 is separated from the fixed arc contact 1, onto the arc occurring when the movable arc contact 4 is separated from the fixed arc contact 1, during a trip operation.
The composite extinguishing method is a method capable of breaking a circuit using a smaller amount of adjusting energy than the puffer method, because the compression chamber 18 and the expansion chamber 19 are separated from each other.
However, the conventional puffer method and composite extinguishing method may have the following problems.
Firstly, in case of the puffer method, a breaking speed is lowered as an inner pressure of the expansion chamber 19 serves as a repulsive force against a breaking operation when a circuit to which a large current has been applied is interrupted. Accordingly, a larger adjusting force is required in the puffer method than in other methods.
Secondly, in case of the composite extinguishing method, the compression chamber 18 and the expansion chamber 19 should be disposed separately. Accordingly, a larger number of components are required in the composite extinguishing method than in the puffer method. Further, since a repulsive force due to increase of a pressure inside the expansion chamber 10 in the puffer method is reduced, a breaking operation can be performed with a smaller adjusting force than in the puffer method. However, this may merely reduce increase of a pressure of the compression chamber 18 due to a piston movement. That is, controlling an inner pressure of the expansion chamber 19 is substantially impossible.
Thirdly, in case of both of the puffer method and the composite extinguishing method, an inner pressure of the expansion chamber is excessively increased. This may cause damage of components inside the extinguishing unit due to heat gas, and may cause scarfing of the contacts and the nozzle.
Fourthly, in case of both of the puffer method and the composite extinguishing method, an inner pressure of the expansion chamber is not sufficiently increased when a circuit to which a small current has been applied is interrupted. This may cause a breaking operation not to be performed.
As a prior art relating to utilization of a pressure of gas occurring from a gas insulating switchgear, Korean Patent Laid-Open Publication No. 10-2012-0002779 (Composite extinguishing type gas circuit breaker for gas insulating switchgear) may be referred.